1. Field of the Invention
The present invention relates generally to the fields of chemical synthesis, imaging, radiotherapy, labeling, chemotherapy, medical therapy, treatment of cardiovascular disease, and treatment of cancer. More particularly, the invention concerns novel methods of synthesis of conjugates for molecular imaging and therapy.
2. Description of Related Art
Regarding synthetic preparations of molecular agents for metal labeling, when such agents are prepared in aqueous (wet) conditions, purification of the agents can sometimes present a problem. Purification in aqueous conditions can be achieved using, for example, size exclusion chromatography, or dialysis with membranes of particular molecular weight cut-offs; for example, dialysis is typically most effective when separating species of molecular weights of 1000 g/mol or higher. However, this method of purification often isolates not only the desired agent, but also any other species that may pass through the membrane. Introduction of impurities into imaging agents may be problematic in future applications of the imaging agents, especially regarding imaging and/or therapeutic uses. For example, if an imaging agent incorporating a radionuclide (the “true” imaging agent) is thought to be pure but actually contains impurities that also incorporate a radionuclide, the proper measurement or detection of the “true” imaging agent may be obscured or rendered false due to the presence of the impurity.
Methods of synthesizing organic compounds in organic solvents and the use of protecting groups, typically offer improvements in the purification of compounds over aqueous purifications. The installation of protecting groups permits various functional groups of intermediates during the synthesis to be protected, and facilitates the purification of those intermediates. Various means of purification using organic solvents allow for separation and isolation of desired compounds, such as imaging agents, with very little impurities. Further, species of molecular weights under 1000 g/mol can often easily be purified using organic chemistry purification methods. In view of the benefits offered by organic synthesis and purification over aqueous purification, methods of organically synthesizing and purifying imaging agents would likely yield agents of higher purity than those obtained via aqueous purification. However, the addition and removal of protecting groups may incur additional costs and reduce efficiency and purify of the final products.
Thus, a need exists for the preparation of these and other agents using synthetic techniques to allow for agents of higher purities to be obtained in a more efficient way.